1. Field of the Invention
The present invention relates to a container closure which admits air to promote a regular and steady flow of liquid from the container.
2. Description of the Prior Art
As liquid is poured from a container, a temporary low pressure area or void develops. The stream of liquid momentarily ceases to flow until air enters the container through the pouring spout to compensate for the low pressure. When this occurs liquid flow resumes. The alternate passage of liquid and air through the same spout causes the flow of liquid to be uneven and irregular, sometimes to such an extent that liquid splashes where it is not wanted.
Container closures exist in the prior art which admit air through an air passage which is separate from the liquid passage or pouring spout. Such closures often include a one-way or check valve in the air passage to prevent liquid entry. U.S. Pat. Nos. 1,278,764 (Seiler); 1,773,475 (Casey); 2,991,897 (Burnett); and 4,407,435 (Harmon) are pertinent in this regard. Despite the presence of the check valve, until the contents of the container are substantially emptied, a somewhat irregular flow of liquid still occurs because the incoming air passes through liquid which seeks escape through the air passage.
Other container closures have been developed which permit air to enter at a point lower or deeper in the container. Consequently, when the container is tipped up the incoming air does not take a liquid path unless the container is absolutely full. A closure of this type is disclosed in U.S. Pat. No. 3,167,220 (Koukal).
The Koukal closure comprises a cork stopper having a dispensing passage, an air passage, and a pipe extension fitted to the stopper in communication with the air passage. An opening is provided in the pipe extension just below the cork stopper to enable air to enter at a point above the liquid level when the container is in an upright position. When the container is tipped up, the opening is located within the liquid. Consequently, incoming air must pass through the liquid and, conversely, since there is no check valve in the pipe extension, liquid can enter through the opening or for that matter also through the lower end of extension, thereby slowing or competing the flow of incoming air.
The Koukal pipe extension is also centrally located. At certain angles of tip of the container, unless it is partially empty, air coming out of the lower end of the extension also must pass through the liquid. As previously indicated, when incoming air and outgoing liquid compete for the same passageway there is a tendency for the flow of liquid to be irregular.
In view of the foregoing, there is a need for a container closure having an elongated tube to provide a passage for air to flow directly into the emptied area at the bottom of an upended container and, in those instances where the container is relatively full or is upright, includes a check valve in the lower end of the liquid from flowing into the tube.